1. Field of the Invention
The present invention relates to a method of and means for replacing corrugating rolls in a single facer.
2. Description of the Prior Art
In a corrugation line for producing corrugated fiberboard, single facers are used to produce single faced corrugated fiberboard. With known constructions of a single facer, a pair of upper and lower corrugating rolls with respective corrugated outer surfaces are disposed in such a way as to engage with each other. A corrugating medium is passed between the rolls in a pressed or engaged manner to be formed into a corrugated configuration or flute, which will be coated at the tips thereof with glue. The single facer also has a pressure roll which is adapted to adhere under pressure the corrugating medium to a linerboard which is fed from a direction opposite to the corrugating medium to produce single faced corrugated fiberboard. Each of the upper and lower rolls employed in the single facer has, as mentioned above, circumferential corrugations extending in the longitudinal direction thereof. The upper roll is freely rotatable and the lower roll is connected to an external source of drive for positive rotation. The upper roll is pressed against the lower roll by means of a spring force or any fluid pressure so that the corrugating medium introduced between the rolls is pressed under appropriate nip pressure to form flutes thereon. The rolls are, in general, made of chrome molybdenum steel which is hardened by quenching or surface-hardened by chromium plating or the like. It is natural, however, that such rolls should have limited durability or service life. After a long period of operation of the single facer, the corrugations formed on the rollers are unevenly worn at the central portions thereof where the medium passes thereover as compared with the longitudinally opposite ends. Such worn rolls cannot provide satisfactory fluting to the corrugating medium. When the service life has ended, it is required to replace the worn rolls whose corrugations are to be reground for reuse. In the prior art single facer, such replacement of a pair of upper and lower rolls has been troublesome because of its construction, and in practice, no less than one or two days are spent on the work. Such time-consuming replacement work results in increased downtime not only of the single facer but also of the whole corrugator line, and consequently the operational efficiency and the production schedule suffer severely. After all, any surface-hardened roll must be periodically replaced because of wear with age, as mentioned above. Therefore, it is a long-pending question and requirement to speed up the roll replacement in the single facer, and this problem has not been completely settled yet.